1. Field of the Invention
This invention relates to a centrifugal barrel finishing apparatus including one or more barrels rotatably mounted on a turnable turret and rotated with turn of the turret so that workpieces contained in the barrels are centrifugally polished, ground or otherwise finished.
2. Description of the Related Art
Japanese Patent Application Publication No. 08019956A published on Jan. 23, 1996 discloses one of conventional centrifugal barrel finishing apparatuses of the above-described type. The disclosed apparatus comprises a pair of upper and lower disks turnable about a vertical axis. Two barrel holding plates are rotatably mounted on the disks respectively. Spring members are mounted so that each holding plate is urged toward the other holding plate side. The barrels are held between the holding plates by a spring force of the spring members so that the barrels mounted on the holding plates are rotated with turn of the holding plates.
Thus, the spring force of the spring members is used for holding the barrels in the conventional barrel finishing apparatuses. However, when each barrel is heavy and the spring force of each spring member is too small relative to a weight of each barrel, the barrels cannot be held reliably. Accordingly, each spring needs to have a large spring force enough to support the barrels. However, when spring members each having a large spring force are used, the spring members are overqualified when light-weight barrels are used.
Therefore, an object of the present invention is to provide a centrifugal barrel finishing apparatus in which a plurality of types of barrels having different weights can be held by an appropriate force.
The present invention provides a centrifugal barrel finishing apparatus comprising a revolving member mounted on a first rotatable shaft so as to be rotated with the first shaft, a barrel provided to be rotated about a second shaft, the barrel having both axial ends, a stopper provided on the second shaft so as to be abutted against one axial end side of the barrel, and a fluid pressure cylinder including a piston and mounted on the second shaft so that the piston pushes the other axial end side of the barrel so that the barrel is held between the stopper and the cylinder.
According to the above-described finishing apparatus, an appropriate holding force can be applied to the barrel since the pressure of the working fluid supplied into the fluid pressure cylinder is changed according to a weight of the barrel.
In a preferred form, the fluid pressure cylinder is disposed to be concentric with the second shaft. A rotation center of the second shaft corresponds with a center of gravity of an assembly of the second shaft and cylinder. Consequently, rotation of the second shaft can be rendered stable.
In another preferred form, the barrel includes a body having an open end and a lid closing the open end of the body, and either one of the piston and the stopper is abutted against the body of the barrel, whereas the other is abutted against the lid of the barrel. Furthermore, the stopper is formed into a shape of a frame surrounding the barrel and has an inner face guiding movement between a first position where the stopper is brought into a sliding contact with a mounting plate so that the barrel is held between the piston and the stopper and a second position where the barrel is released from a held state. In the foregoing construction, either one of the piston and the stopper is abutted against the body of the barrel, where as the other is abutted against the lid of the barrel. Since the piston is rotated together with the stopper, the barrel body and the lid are also rotated together. This construction can prevent slippage resulting from difference between the rotational speeds of the barrel body and the lid.
In further another preferred form, the second shaft has a hollow interior serving as a flow passage of a working fluid, the flow passage communicating with the cylinder. Consequently, the interior of the second shaft can be used more efficiently as compared with a case where the flow passage is provided outside the second shaft.